It is proposed to study the excited state dynamics of tryptophan both on its own, in simple peptides and in proteins. The subnanosecond motions of tryptophyl residues in peptides and proteins will be measured using time dependent fluorescence depolarization techniques based on a continuously working picosecond dye laser. The results will be related to protein structure and function, to recent crystallographic measurements of thermal motion in proteins, and to theoretical models. The photophysics and photochemistry of tryptophan, both in solution and in simple peptides will be studied using picosecond absorption and emission spectroscopy. Changes in the excited state properties will be measured as a function of tryptophan environment and the results applied to the use of tryptophan as an intrinsic probe for protein conformation and structure.